KCS

Sulfide-based (Ca_1-a-bZn_aM_b)S:Eu²⁺,Re³⁺ (M = Mg, Ba, Sr, Re = Pr, Sm, Eu, Gd, Tb) phosphors were synthesized by solid state reaction under a N₂/H₂ reducing atmosphere in a tube furnace. The prepared phosphors excited at 460 nm produced the red luminescence, spanning over the 570 ? 750 nm range. The optimized phosphors were determined as producing the maximum luminescence intensity upon a 460-nm excitation. For the fabrication of light-emitting diodes (LEDs), the optimized phosphors were coated with metal oxides or polymers to overcome their weakness against moisture. The reliability of the luminescence properties of the coated phosphors were examined under a 85/85 environment. Furthermore, the coated red phosphors were cast on a blue InGaN LED chip. The photophysical properties of the phosphor-cast LEDs were investigated as a function of wt% of the red phosphor.